How can I make a library that writes to FILE * write the data to memory instead? (C programming)

Question

I am facing a problem where the C library exposes only an interface that writes the data to a C FILE structure. This means all the data get saved to disk. I want this library to save the data to memory instead.

Is there a way to emulate FILE structure in my code and make it save the data in memory instead? I imagine FILE has various pointers to functions and I could write my own functions and make them allocate memory and on fwrite write the data to memory.

Can this be done?

Thanks, Boda Cydo.

Answer 1

You can have a look at fmemopen.

Answer 2

On a UNIX system, you can use fdopen(3) to get a FILE* that uses a stream you previously opened. Then all you have to do is write some code to read from the other side of that pipe and shovel it into memory.

Answer 3

A portable solution would be to use fmemopen or open_memstream if these functions are available (they've been part of GNU libc for a long time and they were added to POSIX in 2008) and simply write to a temporary file then read back into memory if they're not.